Treating metal shapes



Patented Nov. 3, 1931 UNITED STATES GYoRGY KEBE'KGYARTo, or BUDAPEST, HUNGARY TREATING METAL smns No Drawing. Application filed August 2, 1928, Serial No. 297,108, and in Hungary August 11, 1927.

My invention relates to the treatment of iron and steel with a view to increasing mechanical strength. It -has more particularly reference to the treatment of metallic shapes,

5 such as bars, rods and the like, to be transformed into shafts, -etc.', or tubes, such as gun tubes. It is an object of my invention to provide means whereby the physical and mechanical properties of the metal and of the article made therefrom canbe improved very materially in a particularly simple and effective manner.

It is a well known fact that if a tough and plastic (malleable and ductile) metal, for

instance wrought'iron, is subjected to tensional, compressive or bending strain exceeding its elasticity limit, the material after having been relieved of the strain acting thereon, will -mainly have undergone permanent' changes of form and if the same material is then subjected to further strain,-

its elasticity limit will extend almost up to the strain, to which it had previously been subjected.

I have now ascertained that the yield point of iron and steel can also be materially increased, if the metal is subjected to torsional strain, the increase in strength being substantially proportional to the torsional strain in the original case. I have further found that the increase in strength obtained by subject-v ing the material to .torsional strain offers great advantages as compared to the known method described above.

If it is for instance intended to increase the mechanical strength of a shaft made ofsoft steel, and if the shaft is subjected to elongation by stretching to increase the elasticity two or threefold, the difliculty is encountered that the blank must be elongated 20 to 30 per cent of its original length, its cross-sectional area being at the same time greatly reduced. Similar difliculties would be encountered if the shaft was subjected to compressive strain, for apart from the danger of bending, the blank would have to be upset and shortened at least 20 to 30 per cent of its original length, the cross-sect ional area being increased correspondingly.

In contradistinction thereto the same shaft or other metal shape can be improved as to mechanical strength in avery simple manner by acting thereon with torsional stresses. It is possible to obtain the two or threefold of the original yield point by a single torsion,-

and in this case the cross-sectional area as well as the length of a shaft of circular crosssection will remain practically the same. Even in the case of square or polygonal cross-section the change of cross-sectional area will never amount. to more than a few per cent. The degree. of increase of the yield point depends from the degree of torsional strain beyond the original yield point.

Thus, if it is desired to increase the yield point of a constructional element, such as for instance ashaft, tube or the like made from a suitable material, for instance Wrought iron, it is subjected either before, during or after having attained its final shape, to torsional strain exceeding its original yield point.

I may treat in this manner shafts for power transmission, for vehicles of all kinds including motorcars, flying machines and so on, and gun tubes and other War material, but all other bar or tube-like shapes can be improved in the same manner.

' For instance, if a shaft for power transmission shall be treated according to this invention, a preformed wrought iron bar is twisted either in the cold or at a moderate temperature (below 600 (3.), eitheronce or several times, until the yield point of the material has been more or less exceeded whereupon the article under treatment is relieved of the strain and is subjected to further treat- I ment to bring it into final shape.

The great advantag- 1i this invention consists therein, that owing to tl: increased yield point the mass of the articles treated can be reduced materially without any danger, for instance-the weight of a shaft for power transmission may be reduced to two' thirds of the weight of an ordinary shaft used under the same load. Obviously this reduction in weight will be accompanied by a reduction in the weight of the bearings. The reduction in weight will be particularly loo advantageous in the case of shafts for use in combination with vehicles.

'Variouschanges may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof;

I claim The method of improving the physical and mechanical properties of iron and steel comprising subjecting the article to be treated at a temperature below 600 C. to torsional strain beyond the yield point of the metal and thereafter relieving same of the strain.

In testimony whereof I aifix my signature.

GYGRGY KEREKGYARTO. 

